Apparatus for making granular superphosphate



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. 8, 1942. .M sHoELD APPARATUS FOR MAKING GRANULAR SUPERPHSPHATE Filed June 15, 1958 Patented Dec. 8, 1942 i UNITED STATE marinus Fon SUPEBPHOSPHATE Mark Shoeld,

Davison Chemical Baltimore, Md.,

Corporation,

assignor to The Baltimore, Md.

museum im 15. 193s, serial Na.. 213,926

ZCiaims.

This invention relates to the manufacture o! granular superphosphate, and to an improved apparatus therefo In the manufacture of granular superphos-f phate. `a lpreferred form of process is one in which the superphosphate, with suflicient water, is agitated to produce agglomerated particles. These agglomerated particles are then subjected to a drying step under 4further agitation to form hard, dry granules. Ordina this ytype of process is carried out in apparatus which comprises a rotary drum in which the particles are agglomerated. Particles thus agglomerated are subjected to the drying step in another rotary heated drum. Another form of process comprises agglomerating or conditioning and then drying in the same rotary drum in different sections of the drum. An aqueous medium may be added to produce the desired initial moisture content to assistinthe agglomeration.

The granular superphosphate obtained comprises hard, dry, globoid, nodular, encrusted and indurated particles having several timesV the crushing strength of ordinary fully cured den superphosphate.

When fresh superphosphate directly from the den is charged into the conditioner of the granulating unit, there is in many instancessufilcient variation as to physical condition of the densuper to make this l operation impractical. The dimculty is that at times the agglomeration in the conditioner is excessive so that large lumps dorm, and occasionally a ,clayey mass is formed. This causes trouble due to sticking of the material in the conditioner and the dryer, and the ilnal material is too large and non-uniform as to size and moisture content. When the madryer is too large the amount of dust produced during the subsequent milling op- U-p to the time of this invention it was necessary to .put the fresh super into preliminary storage or to rasp and aerate it, so as to allow proper control of particle size in the conditioner. This procedure entailed, of course, considerable extra cost due to the rehandling of the material and storage facilities required.

By means of this invention, fresh densuper can be transferred directly from the den to the conditioner, and the particle size from the conditioner can be controlled within the accuracy that the commercial application of the process requires. This is accomplished by feeding in a determined amount of dry material end of the conditioner where it enters with the `'fresh densuper.

so matic illustration of a form It is therefore important, if maximum capacity is desired, to avoid storing or rasping Vthe super prior to granulation. Using this invention it is possible to do so. In other words there only saving due to elimination of handling, rasping and storing charges-but the capacity of the granulating unit is also increased.

Any dry or reasonably dry material may be used as the additive, as for instance sand. if it is required to cut the concentration of P20 in the final product. Well cured densuper may be used. 'I'he most suitable material is, however, classifier dust, which is obtained in the following manner.

The granulated material from the unit goes to storage for a minimum of approximately 10 days. When shipping granular` superphosphate, the material from storage is passed over a screen to eliminate any .overs This oversize goes to a mill, is crushed, and is returned to the screen. The entire product from the screen is passed through a pneumatic classifying system. where substantially all fines are removed. The dust free material is discharged into bags ready for shipment. The amount of classifier dust may vary -from 10 to 20% of the total production.

Instead of using .pneumatic classification, double screening may be used. The net result will however be approximately the same.

`Il'he classifier dust may be sold by itself or mixed with regular densuper and sold as run of pile or cut to 16%. .The advantage of using it back in the granulating system is however quite considerable as has been pointed out above. Moreover. the dust has a high percentage of available PnOs.

.As an addition substance, dry phosphate rock may be used and this material is particularly suitable when it is desired to make cut superpnosphate in territories wnere it is undesirable to aad sand as iiller. An additional advantage is obtained when the ground pnospnate rock is usedy Ibecause some of the P205 in this becomes available without the use of any extra sulpnuric acid. In other words when pnospnate rock has to be used to produce a cut grade of granular superphosphate there is a distinct acid economy obtained. f I

Among the objects of the invention are to reduce handling, save time and cost of production, and insure a more uniform product.

Another object is to provide an apparatus which is simple, inexpensive, eicient to operate, and easy torepair and replace.

Other objects will be apparent from the description of the apparatus used and the process as set forth.

The single ilgure of the drawing is a diagramof apparatus which is not I may employ, section.

Referring to the drawing I have shown a conditioner I and a drier 2. The conditioner I comprises a hollow metallic cylinder 3 having rings 4 thereon which are adapted to roll on rollers 5 mounted on supports 5. 'I'here are a plurality of rollers at each ring 4. The metallic cylinder 3 is rotated by means of a ring gear 5 driven by a pinion 6 mounted on the shaft of a motor 1. It is to be understood that reduction gearing may be employed between the motor and theV pinion 6', but for purposes of illustration nosuch reduction gearing is shown. The metallic cylinder is provided with a partially closed end 8 having an aperture 9 therein into which sticks a spout I0 of a hopper II. A slat conveyor or belt I2, which is adapted to be driven from some source of power, not shown, conveys fresh den superphosphate I3 from a superphosphate hopper I4. The superphosphate is delivered to the hopper I4 by means of a clam shell bucket which takes the material directly from the den, or some other means of transportation may be employed.

'I'here is a sliding door I5 provided in one side of the hopper I4 adjacent an aperture I6. The door I5 is provided with a handle I1. By raising or lowering the door I 5, the amount of fresh den superphosphate I3 which is conveyed by the slat conveyor I2 can be determined.

Fed also into the hopper II is a dry, nely divided material I8 which may be sand, fully cured superphosphate, classifier dust, ground phosphate rock, or some other similar material.

'I'his material I8 is fed by means of a screw conveyor I9 operating in a conveyor box 20 located at the bottom of a hopper 2I. The screw I9 is rotated by means of a, gear 22 meshing with a pinion 23 driven by a variable speed motor 24.

Adapted to discharge an aqueous medium into the conditioner I are pipes 25 having nomles 26. Valves 21, which may be manually operated by an operator control the amount of aqueous medium discharged into the interior of the conditioner I.

Mounted on an instrument panel 28 are meters 29 and 30. The meter 29 is connected electrically to a pyrometer 3I located in a refractory lined combustion furnace 32, heated `by a -gas burner 33. The meter 30 is electrically connected to a thermometer 34 .which is located in a discharge breeching 35 which covers the end of a rotary cylinder 36 which forms the drier 2. The temperature of the hot gases entering the drier 2 and leaving the drier 2 are readable on the meter faces 29 and 30 respectively.

Mounted on the instrument panel 28 is a nood light 31 which is directed into the open end of the conditioner I.l A supporting platform 38 is located adjacent the open end of the conditioner I. The conditioner I is slanted downward from the end into which the fresh den superphosphate is discharged. An operator standing on the platform 38 at all times can visually inspect, by means of the floodlight 31, the interior of the conditioner I, and regulate by means of valves 21 the condition of the material in the conditioner I. The operator must be present on the platform at all times and by adjustment of the regulating valves 21, he maintains a constant physical condition of the material leaving the conditioner and entering the drier.

In the operating :door is a trap door 40 which is on hinges and provides easy access to a cleanthe apparatus being shown in cut door 4I in a water-jacketed chute 42. A bailie 43 prevents the conditioned agglomerated particles from falling out of the upper end of the water-jacketed chute 42.

The water-jacketed chute 42 is provided with a water jacket 44 in which cooling fluid is circulated to prevent over-heating of the chute. The connections for sending the uid through the water jacket are not shown. The lower end of the chute discharges into the upper end of the drier 2, which has an aperture 45 into which the lower end of the chute projects.

The rotary cylinder 36 drier is slanted from the horizontal and is prothe shaft of a motor 5I. Here again reduction gearing may be used if desired, but such a. construction is not shown in order to simplify the illustration of the apparatus.

The discharge breeching 35 is connected to -a pipe 52 which leads to the suction side of a blower The discharge breeching 35 is provided with a discharge chute 56.. Mounted on some other conveying mechanism.

Fresh unrasped super -I3 direct from the den is charged into hopper I4. The densuper may as an example have the following average composition:

Per cent Moisture. 10.56 Total P205 20 03 InSOl. P205 3.04 Avail. P205 16.99

Moisture Total P205 21.3 InsOl. P205 by weight. added to the material tor on the platform elimination in the dryer is asoassa in the conditioner. through sprays Il averages approximately 1.2%. This doesnot mean that there is a uniform addition, because-the operagives constant attention to the physical condition of the material in the conditioner and regulates the amount of water by means `of `valves 21, so that every minute of the day visual observation governs the proper physical condition of the material going to the dryer. The instant water` additions may vary from practically nothing to 2% or more. The range is generally from about 563% to 2%.

This water addition is so critical for proper operating conditions that a small fraction of a percent will produce a major change of physical condition of the material. A

The average addition of about 1.2% mentioned above, withl the given average composition of super and classifier, dust, means that the material from the conditioner to the dryer has an average moisture content practically identical with that of the super fed or i/i. This clearly brings out the point that the classifier dust addition is for the purpose of regulation, which is of paramount practical importance for the successful commercial carrying out of the process.

The granulated super from the dryer has the following composition:

Per cent Moisture 5.15 Total P 21.08 Insol. PiOs 2.75 Avail. PzOs 18:33 This material is allowed to stand in storage lfor a minimum of approximately i0 days. After passing through the shipping unit theflnal material inthe bags analyzes as follows:

Per cent vMoisture 1.67 Total PaOs 21.44 Insol. PaOe 1.18 Avail. P205 20.26

'is the standard commercial grade that has been established for granular superphosphate.

In connection with the moisture changes in the material during the process, the following is of interest.

The fresh densuper has a moisture content of about 10i/2%. 'I'he material from the conditioner to the dryer has the same average moisture content or 10V2%. The granulated super from the unit shows about 5% moisture. The moisture therefore about .5l/3%. The shipping material has a moisture-of about 195%. There is therefore an apparent difference of 31/2% moisture between the material from the granulating unit and the material as shipped. Careful investigation has shown that the true moisture loss between these two points is only 1%% and is due to handling and transfer through the shipping unit. The balance of 2%` is changed from free water-to fixed water, that is chemically bound water that does not go off at 100 C. by the standard method of moisture determination.

The remarkable efficiency of the process from Set forth in a somewhat simpler manner on .Thismaybewrittem `phatic fertilizer material comprising den superpnosphate.

ofaeidulationdurlngthevarlousstepeoftheprocess the result is as follows: t

' Per cent aeidulation Super from den entering conditioner 84.7 Material from dryer. 87.0 Material shipped. 94.5 The definition for per cent acidulatlonWis the availablePsOsasapercentageofthetotalPaOs.

nt available P, Q percent total h, X By the accurate control of the moisture content andthegeneralconsistencyofthefreshden the agglomerating step, a subsizewitharelativelysmallpercentageofnnesor` oversised `Whilelhiweshovvnvltprocessandapparatil which are illustrative of my invention, it is to be understoodthatlamtobelimitedonlybythe scope of the appended claims and the showing of the prior art.

I claim: 1. An apparatus for producing granularphosa combined conditioning and agglomerating rotatable drum, the longitudinal axis of said drum being inclined t to the horizontal, a feed hopper mounted adjacent the high end of said drum and adapted to introduce material thereto, means for supplying fresh den superphosphate of varying moisture content to said hopper, means for supplying finely divided' dry material to said hopper to condition the fresh the low end of said drum being open to permit inspection and discharge of the conditioned material passing therethrougma plurality of aqueous medium spraying means positioned at longitudinally spaced regions in the upper portion of said drum, a separate conduit extending from each spraying means out through theopen endofthedrum,andvalvemeansineach conduit and provided with control means positioned adjacent the open end of the drum within reach of an operator while inspecting the contents ofthedrumthroughtheopenendtoenablesaid operator to control the amount of aqueous medium sprayed into and the condition of the material within said drum.

2. An apparatus for producing granular phosphatic fertiliser material comprising a combined conditioning and agglomerating rotatable drum, the longitudinal axis of said drum being inclined to the horizontal, a feed hopper mounted adjacent the high end of said drum and adapted to introduce material thereto, means for supplying fresh den superphosphate of varying moisture content to said hopper, means for supplying nnely divided dry material to said hopper to condition the fresh den superphosphate, the low end of said drum being open to permit inspection and discharge of the conditioned material passing therethrough, a plurality of spray means extending from the low end of said drum to separate points therein, valve means in each of said spray means to control the supply of moisture thereto, a rotatable drying drum mounted for rotation about an inclined horizontal axis, a feed chute mounted adjacent the discharge end of said conditioning and agglomerating drum and having a discharge thebasisofpercentsge 7s spout to deliver the discharged materialto the upper end of said drying drum, a heating chamcharge breeching and from said lower end oi' said ber mounted at the high end of said drying drum drying drum. said breeching having a discharge and closing the upper end of said drying drum to opening for solids in its lower portion, and a ciothe atmosphere, a burner mounted in said heating sure for said solids discharge opening tending to chamber for supplying hot gases to said vdry- 5 close said opening to prevent air being drawn ing drum, a discharge breaching at the lower end therethrough and to cause hot gases to be drawn of said drying drum, a suction fan for withdrawthrough the drying drum by the suction fan.

ing gases from the upper portion of said dis- MARK SHOELD. 

